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Re: Overboosting need help. Posted by Ari [Email] ![]() ![]() In Reply to: Re: Overboosting need help., Jack, Wed, 14 Jan 2009 10:07:28 Members do not see ads below this line. - Help Keep This Site Online - Signup |
The BPC valve has two coils. When energized, these coils create a magnetic field that moves the valve. The controller has two transistors, each one controlling one coil. The controller pulses the coils. When the pulses are the same width in both coils, the valve is in the center. When by hitting one coil with wider pulses than the other, the coil with the wider pulses has a stronger magnetic field, and the valve moves that way.
Depending on which coil/transistor fails, the valve will stay more in one direction than another. So depending on the blown transistor, you'll get overboost or base boost.
With the older APC solenoid (two wire), ON was full boost, and OFF, due to a bad coil, broken wire, or blown transistor, was base boost. But not on your car.
It would be interesting to measure the resistance of the coils on your old BPC. They should be ~ 3.0 ohms each. If one is shorted, it can kill the transistor driving it. But the BPC can also read just fine, and the transistor just died.
Do some Google searches - there are folks that have opened up the box and replaced the transistor.
posted by 192.249....
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